scholarly journals First Study on Ammonia Spray Characteristics with a Current GDI Engine Injector

Fuels ◽  
2021 ◽  
Vol 2 (3) ◽  
pp. 253-271
Author(s):  
Ronan Pelé ◽  
Christine Mounaïm-Rousselle ◽  
Pierre Bréquigny ◽  
Camille Hespel ◽  
Jérôme Bellettre
Keyword(s):  
Physical Parameters ◽  
Combustion Engines ◽  
Free Energies ◽  
Spray Characteristics ◽  
Penetration Length ◽  
Gdi Engine ◽  
Mitigate Climate Change ◽  
Semi Empirical ◽  
A Current ◽  
Ammonia Injection

Using carbon free energy sources is one of the keys to mitigate climate change. Hydrogen promises to be one of these carbon free energies, but its storage is difficult and expensive. Ammonia, however, is interesting as it can store hydrogen safely and can be used in combustion engines instead of hydrocarbon fuels. In this experimental work, the spray characteristics of ammonia under different air densities and temperatures were investigated in constant volume and were compared to a biofuel, ethanol, and a common fuel, gasoline. The Schlieren technique was used to capture images of liquid and liquid + vapor spray. The penetration length, the angle near the injector and the angle at half-penetration length were measured. The results show that the spray geometry of ammonia differs from that of the other fuels and that its sensitivity to air density and temperature is greater. The flash boiling condition at ambient temperature was explored for ammonia and indicated a wider spray at half-penetration length at phase change. Moreover, a semi-empirical correlation for penetration length as a function of physical parameters was found with a high accuracy for the global spray. These experimental data provide the first information about ammonia injection with a current spark-ignition GDI injector.

Prediction of Hydraulic Conductivity of Fly Ash Built-in Mineral Sealing Layers

2017 ◽  
Author(s):  
Mariola Wasil
Keyword(s):  
Fly Ash ◽  
Hydraulic Conductivity ◽  
Laboratory Tests ◽  
Physical Parameters ◽  
Low Permeability ◽  
Empirical Formulas ◽  
Semi Empirical ◽  
Sealing Layer ◽  
Compaction Method

Mineral barrier protects the groundwater and soil from contamination by insulating the leakage of harmful substances from landfill. One of the most important parameters, which decides about usefulness of material to built-in sealing layers, is hydraulic conductivity. Researchers have conducted investigations with the possibility of utilising fly ash as a mineral sealing layer material, which is justified by its low permeability and other properties. It is known that laboratory tests of hydraulic conductivity are often long-term and require expensive equipment. Therefore, to avoid this, researchers trying to assess permeability of tested material with empirical or semi empirical formulas. The aim of the paper is to compare the results of hydraulic conductivity of fly ash obtained from the laboratory tests and from estimation using different empirical formulas. Fly ash was compacted by the Standard Proctor compaction method at the optimum moisture content. The results obtained from empirical equations were variable. It was observed that the Kozeny-Carman formula and other, based on a few physical parameters of the soil, gave better results in prediction of hydraulic conductivity of fly ash than equations based on only one parameter.

Calculation of jet characteristics from hydrocode analysis

2019 ◽  
Author(s):  
Justin C. Sweitzer ◽  
Nicholas Peterson ◽  
Scott Hill
Keyword(s):  
System Integration ◽  
Shaped Charge ◽  
Physical Parameters ◽  
Stretch Rate ◽  
Time Calculation ◽  
Semi Empirical ◽  
Analytic Models ◽  
Shaped Charge Jet ◽  
Jet Characteristics ◽  
Breakup Time

Abstract The penetration performance of a shaped charge jet is affected strongly by factors such as straightness, stretch rate, and breakup time. Straightness is related to manufacturing tolerances, assembly techniques, and system integration features. Stretch rate and breakup time are controllable features of charge design. A higher stretch rate is desirable for short standoff performance. The stretch rate is easily altered by a change of explosive or modification of the angle with which the detonation wave sweeps the liner surface, however, an increased stretch rate generally results in a decreased breakup time. Many of the recent gains in shaped charge performance have been made possible by increasing the effective breakup time of the jet. Several models exist for calculating breakup time. They include analytic models, such as Chou & Carleone’s dimensionless strain rate model, and empirical or semi-empirical models such as Walsh’s theory and those proposed by Pearson, et al. These models can be applied to raw hydrocode calculation data and used to determine a Jet Characterization (JC) file. The JC file can then be used to perform further calculations, such as Penetration Versus Stand Off (PVSO) curves. This paper details adaptation of the Chou & Carleone model for predicting breakup time using hydrocode data. The hydrocode is used to determine the physical parameters of the jet which are then extrapolated back to a virtual origin for breakup time calculation. This results in a model that is design independent, relying on hydrocode determination of jet variables. The model implementation will be discussed, and comparisons of predicted jet characteristics will be made to test data for several charge geometries.

Scaling liquid penetration in evaporating sprays for different size diesel engines

2019 ◽  
Vol 21 (9) ◽  
pp. 1662-1677 ◽  
Author(s):  
Xinyi Zhou ◽  
Tie Li ◽  
Yijie Wei ◽  
Ning Wang
Keyword(s):  
Diesel Engine ◽  
Diesel Engines ◽  
High Speed ◽  
Scaling Laws ◽  
Fuel Injection ◽  
Pollutant Emissions ◽  
Liquid Penetration ◽  
Spray Characteristics ◽  
Penetration Length ◽  
Air Mixing

Scaled model experiments can greatly reduce the cost, time and energy consumption in diesel engine development, and the similarity of spray characteristics has a primary effect on the overall scaling results of engine performance and pollutant emissions. However, although so far the similarity of spray characteristics under the non-evaporating condition has been studied to some extent, researches on scaling the evaporating sprays are still absent. The maximum liquid penetration length has a close relationship with the spray evaporation processes and is a key parameter in the design of diesel engine spray combustion system. In this article, the similarity of maximum liquid penetration length is theoretically derived based on the hypotheses that the spray evaporation processes in modern high-pressure common rail diesel engines are fuel–air mixing controlled and local interphase transport controlled, respectively. After verifying that the fuel injection rates are perfectly scaled, the similarity of maximum liquid penetration length in evaporating sprays is studied for three scaling laws using two nozzles with hole diameter of 0.11 and 0.14 mm through the high-speed diffused back-illumination method. Under the test conditions of different fuel injection pressures, ambient temperatures and densities, the lift-off law and speed law lead to a slightly increased maximum liquid penetration length, while the pressure law can well scale the maximum liquid penetration length. The experimental results are consistent with the theoretical analyses based on the hypothesis that the spray evaporation processes are fuel–air mixing controlled, indicating that the local interphase transports of energy, momentum and mass on droplet surface are not rate-controlled steps with respect to spray evaporation processes.

scholarly journals Development of an Optical Sensor Head for Current and Temperature Measurements in Power Systems

2013 ◽  
Vol 2013 ◽  
pp. 1-12 ◽  
Author(s):  
Fábio V. B. de Nazaré ◽  
Marcelo M. Werneck ◽  
Rodrigo P. de Oliveira ◽  
D. M. Santos ◽  
R. C. Allil ◽  
...  
Keyword(s):  
Power Systems ◽  
Transmission Lines ◽  
Laboratory Tests ◽  
Single Point ◽  
Physical Parameters ◽  
Measurement Reliability ◽  
Point Temperature ◽  
Sensor Head ◽  
Demodulation Method ◽  
A Current

The development of a current and temperature monitoring optical device intended to be used in high-voltage environments, particularly transmission lines, is presented. The system is intended to offer not only measurement reliability, but to be also practical and light weighted. Fiber Bragg gratings (FBGs) are employed in the measurement of both physical parameters: the current will be acquired using a hybrid sensor head setup—an FBG fixed on a magnetostrictive rod—while a single-point temperature information is provided by a dedicated grating. An inexpensive and outdoor-suitable demodulation method, such as the fixed filter technique, should be used in order to improve the instrumentation robustness, avoiding expensive and complex auxiliary electronics. The preliminary results for laboratory tests are also discussed.

scholarly journals Geophysical investigation of landslides : a review

2007 ◽  
Vol 178 (2) ◽  
pp. 101-112 ◽  
Author(s):  
Denis Jongmans ◽  
Stéphane Garambois
Keyword(s):  
State Of The Art ◽  
Geophysical Methods ◽  
Temporal Variations ◽  
Physical Parameters ◽  
Geophysical Investigation ◽  
Current State ◽  
Image Characteristics ◽  
Geophysical Techniques ◽  
Shallow Geophysics ◽  
A Current

Abstract In the last two decades, shallow geophysics has considerably evolved with the emergence of 2D spatial imaging, then 3D spatial imaging and now 4D time and space imaging. These techniques allow the study of the spatial and temporal variations of geological structures. This paper aims at presenting a current state-of-the-art on the application of surface geophysical methods to landslide characterization and focuses on recent papers (after 1990) published in peer-reviewed international journals. Until recently, geophysical techniques have been relatively little used for the reconnaissance of landslides for at least two main reasons. The first one is that geophysical methods provide images in terms of physical parameters, which are not directly linked to the geological and mechanical properties required by geologists and engineers. The second reason shown through this study probably comes from a tendency among a part of the geophysicists to overestimate the quality and reliability of the results. This paper gave the opportunity to review recent applications of the main geophysical techniques to landslide characterisation, showing both their interest and their limits. We also emphasized the geophysical image characteristics (resolution, penetration depth), which have to be provided for assessing their reliability, as well as the absolute requirements to combine geophysical methods and to calibrate them with existing geological and geotechnical data. We hope that this paper will contribute to fill the gaps between communities and to strength of using appropriate geophysical methods for landslide investigation.

scholarly journals A numerical study of the effects of injection rate shape on combustion and emission of diesel engines

2014 ◽  
Vol 18 (1) ◽  
pp. 67-78 ◽  
Author(s):  
Zhixia He ◽  
Tiemin Xuan ◽  
Yanru Xue ◽  
Qian Wang ◽  
Liang Zhang
Keyword(s):  
Diesel Engines ◽  
Numerical Study ◽  
Numerical Models ◽  
Injection Pressure ◽  
Injection Rate ◽  
Spray Characteristics ◽  
Penetration Length ◽  
Emission Performance ◽  
Injection Duration ◽  
Hump Shape

The spray characteristics including spray droplet sizes, droplet distribution, spray tip penetration length and spray diffusion angle directly affects the mixture process of fuel and oxygen and then plays an important role for the improvement of combustion and emission performance of diesel engines. Different injection rate shapes may induce different spray characteristics and then further affect the subsequent combustion and emission performance of diesel engines. In this paper, the spray and combustion processes based on four different injection rate shapes with constant injection duration and injected fuel mass were simulated in the software of AVL FIRE. The numerical models were validated through comparing the results from the simulation with those from experiment. It was found that the dynamic of diesel engines with the new proposed hump shape of injection rate and the original saddle shape is better than that with the injection rate of rectangle and triangle shape, but the emission of NOX is higher. And the soot emission is lowest during the late injection period for the new hump-shape injection rate because of a higher oxidation rate with a better mixture between fuel and air under the high injection pressure.

Thermodynamic Analysis of Nb-Cr Powders of Mechanical Alloying

2007 ◽  
Vol 26-28 ◽  
pp. 181-184
Author(s):  
Xiao Wu Nie ◽  
Shi Qiang Lu ◽  
Ke Lu Wang
Keyword(s):  
Solid Solution ◽  
Amorphous Alloy ◽  
Mechanical Alloying ◽  
Milling Time ◽  
Sem Analysis ◽  
Free Energies ◽  
Planetary Ball Milling ◽  
Cr System ◽  
Semi Empirical ◽  
Form Solid Solution

In this study, Nb-Cr binary mixtures were prepared by mechanical alloying. And mechanical alloying process of mixed Nb-Cr(1:2) powders was studied, and the phases of milling powders analyzed by XRD and SEM. It has been found that the powders form solid solution first, then amorphous phase appeared gradually and crystallization of amorphous takes place with the different milling time. A thermodynamic model of MA of Nb-Cr system was developed based on Miedema Semi-experimental theory to explain the phase transformations of Nb-Cr system during milling. Using Miedema semi-empirical model the free energies of the ordered Laves-phase NbCr2 intermetallics, solid solution and amorphous alloy were calculated. From XRD and SEM analysis of Nb/2Cr powders prepared by mechanical alloying in a planetary ball milling, it was found that the calculated results were in accordance with the experiments.

scholarly journals Towards an Urban Vibrancy Model: A Soundscape Approach

2018 ◽  
Vol 15 (8) ◽  
pp. 1712 ◽  
Author(s):  
Francesco Aletta ◽  
Jian Kang
Keyword(s):  
Laboratory Experiment ◽  
Predictive Model ◽  
Environmental Design ◽  
Physical Parameters ◽  
Research Needs ◽  
The Mean ◽  
Urban Contexts ◽  
The Uk ◽  
Presence Of People ◽  
A Current

Soundscape research needs to develop predictive tools for environmental design. A number of descriptor-indicator(s) models have been proposed so far, particularly for the “tranquility” dimension to manage “quiet areas” in urban contexts. However, there is a current lack of models addressing environments offering actively engaging soundscapes, i.e., the “vibrancy” dimension. The main aim of this study was to establish a predictive model for a vibrancy descriptor based on physical parameters, which could be used by designers and practitioners. A group interview was carried out to formulate a hypothesis on what elements would be influential for vibrancy perception. Afterwards, data on vibrancy perception were collected for different locations in the UK and China through a laboratory experiment and their physical parameters were used as indicators to establish a predictive model. Such indicators included both aural and visual parameters. The model, based on Roughness, Presence of People, Fluctuation Strength, Loudness and Presence of Music as predictors, explained 76% of the variance in the mean individual vibrancy scores. A statistically significant correlation was found between vibrancy scores and eventfulness scores, but not between vibrancy scores and pleasantness scores. Overall results showed that vibrancy is contextual and depends both on the soundscape and on the visual scenery.

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